Q432: How do you solve performance corner cases while using context? - React & Modern Frontend (445 Qs)

The context uses reference identity to determine when to re-render, there are some gotchas that could trigger unintentional renders in consumers when a provider’s parent re-renders.

css

For example, the code below will re-render all consumers every time the Provider re-renders because a new object is always created for value.

javascript

    class App extends React.Component {
      render() {
        return (
          <Provider value={{ something: "something" }}>
            <Toolbar />
          </Provider>
        );
      }
    }

vbnet

This can be solved by lifting up the value to parent state,

javascript

    class App extends React.Component {
      constructor(props) {
        super(props);
        this.state = {
          value: { something: "something" },
        };
      }

      render() {
        return (
          <Provider value={this.state.value}>
            <Toolbar />
          </Provider>
        );
      }
    }